Need to change volume to hear music, help needed

Hi,

I have a SB Touch connected to a Sonos Play 5 via line in and control music via iPeng. The problem I have is that I when I start with a low volume (under 30% or so), I need to increase the volume level in iPeng before I can hear any music from the Sonos. When I then change the volume back to the same level as when I started the music on the Sonos plays fine.

Can someone help me out why this is happening? Does LMS needs a minimum volume level to pass it through to speakers? When I press play iPeng shows that the song started and the song will play on, but I can only start hearing any music after increasing the volume level...

Any help appreciated!